Chapter 54 of 2363 min read
Ohm's law, resistivity, temperature dependence
Why this is asked: Resistivity is a property of the material only — stretching a wire to twice its length doubles R (since R = ρl/A) but leaves ρ itself unchanged, and resistivity rises with temperature for metals but falls for semiconductors.
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- •A wire of resistance is cut into 8 equal pieces. From these pieces two equivalent resistances are made by adding four of them together in parallel. Then these two sets are added in series. The net effective resistance of the combination is:
- •A wire of length and resistance is divided into 10 equal parts. The first 5 parts are connected in series while the next 5 parts are connected in parallel. The two combinations are again connected in series. The resistance of this final combination is:
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